The present invention relates to a photovoltaic cell, which can be used in the manufacture of solar cells.
In the field of solar cells the aim is to produce equipment having a low cost, but an acceptable conversion efficiency. In practice a compromise is made between these partly contradictory requirements.
Relatively high conversion efficiencies of approximately 20% can be obtained by using as the active layer a monocrystalline material formed by a semiconductor of the III-V type, such as GaAs or InP. However, this leads to high costs and is more suitable for solar generators using optical solar flux concentration means then for standard uses.
More recently it has been proposed to reduce the cost by using thin polycrystalline layers deposited on inexpensive graphite or molybdenum supports.
Thus, a solution has been described in which a layer of polycrystalline germanium is placed between the support and the active polycrystalline gallium arsenide layer, which has the effect of increasing the size of the particles of the polycrystalline active layer deposited by epitaxy on the germanium. Conversion efficiencies of approximately 5 to 6% are obtained with such a composite support (germanium-coated molybdenum). Germanium could be replaced by another material with a lattice parameter relatively close to that of the material of the active layer in order to permit epitaxy.
The object of the invention is either to permit an improvement in the efficiency, accompanied by the same costs for the starting material and other components, or a reduction in the price of the cell, particularly by reducing the starting material costs, whilst maintaining an identical efficiency.